Rotomoulding is a moulding technic of plastic material by rotation in an oven, allowing to shape it without bonding or welding. Four stages are part of the rotomoulding process:
Polyethylene (plastic) in powder form is inserted in a mould to to replicate the internal form of this mould of which the volume can go from 0.1L to 50,000L. The material used for our tanks is carefully selected to grant a unique resistance to our products. Before each cycle, the powder quantity is calculated depending on the thickness required. The rotomoulding moulds are hollow and made in two removable parts, mainly in steel plates, magnesium or aluminium. Aluminium is the most commonly used for rotomoulding as it offers a better thermal conductivity and its lifespan is higher.
Once loaded and closed, the mould rotates following two orthogonal axis during a heating step. The head is normally brought by gas or fuel burners: hot air circulation in the oven.
In this step, the mould, still in rotation, is removed from the oven to be cooled off. Water, cool air or a combination of both («mist spraying») allow to cool off the mould and thus of the melted material.
The part is finally demoulded when the internal air temperature is low enough, which means when the part is well strenghened. The connexions are then opened (between the lower and the higher part of the mould) and we extract the part which corresponds exactly to the internal architecture of the mould. For the thermoplastics, it is interesting to remove the piece of the mould while still hot to benefit from its malleability.